Radio signaling circuit



W. D. LOUGHLIN RADIO SIGNALING CIRCUIT Nov. 19, .1929.

Filed March 5. 1925 I l l l I l I I I I I per F""Z I. i 57$? I 6 Patented Nov. 19, 1929 v UNITED RADIO srennnrne omcnrr Application filed March 5, 1925. Serial No. 13,249.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AIv'IEII'lITEID APRIL 30, 1928; 370 0. G. 757) My invention relates broadly to radio receiving circuits and more particularly to radio compass receiving circuits.

The object of my invention is to provide an 5 economic and efficient means for tunlng the loop circuit of a radio compass system over a very broad band of frequencies.

Further objects of the invention will appear more fully hereinafter.

' 0 The invention consists substantially in the construction, combination, location, and relative arrangement of parts and circuit arrangements associated therewith, as will be more fully hereafter set forth, as shown by 15 the accompanying drawings and? finally pointed out in the appended claim.

Reference is to be had to the accompanying drawings forming a part of this specification in which like reference characters indicate 26 corresponding parts throughout the several views and in which Figure 1 represents the preferred embodiment of my invention and Figure 2 shows a modification in wh ch the shunted inductance is made variable and 1n "25 which the variable tunin condenser as is used in the conventional radio compass circuits,

may be fixed.

In the conventional radio circuit, comprising a fixed coil and associated variable coneo denser the tuning ratio, (maximum to mini-' mum wavelength or frequency) is of the order of two and one-half to one, (2 1) and only by skillful disposition of connecting leads to reduce the residual capacities is 1'0 915 possible to extend the tuning range to a three to one (3:1) ratio.

The present practice of increasing the width of the band of frequencies to which a radio compass will respond is either to add "46 inductance in serieswith the collector system or provide a switching arrangement to short circuit or cut out turns in the collector system or to add capacity in parallel with the tuning v capacity. The advantages of my lnventlon 45 will be understood by those familiar with the artwhen considerationis givento the fact that the reception factor or the efliciency reception of a radio compass system is directly proportional to the area enclosed by the coil system 51) and the number of turns and is inversely proportional to the radio frequency resistance and the total shunt capacity. When the method of adding inductance in series with the loop system is used, the area and-number of turns of the loop system is limited to a value such that when the series inductance is short-circuited the system will respond to the' shortest contemplated wavelength; any increase in wavelength'range requires induc tance in series thereby increa'singthehigh fre quency resistance of the circuit. Besides this, the added inductance does not increase the coupling with the flux of the observated wave. Furthermore, adding inductance in series will cause the collector system to become elec trically unsymmetrical and will require a compensating device for the collector system to indicate the'true direction of the propagated wave. Itis possible to add inductance in each lead of the collector system but such meanswill require a most careful selection of inductance and a most complicated switching arrangement and usually requires a variable compensating device? Short circuiting or opening turns of the loop system introduces'a dead-'endeffect of the turns thus eliminated and unless: complicated switching arrangements are used the'electrically symmetry of the loop 'is destroyed and compensators are required. Adding capacity in parallel with the tuning capacity decreases the efficiency of the system as the voltage variation delivered to the receiver or amplifier depends upon the. inductance capacity ratio. The" larger the capacity the smaller the voltage variation.

My invention provides means for avoiding the disadvantagesoutlined above a'nd-is'based upon the principle-that the resultant induc tance of two inductances connected in parallel is directly proportional totheir product and inversely proportioned to their sum. By adding an inductance in parallel with the loop systemthe tuning range of theloop system-is shifted to a different band of wavelengths or,

by adding a variable'inductance in parallel Q6 and keeping the capacity of the loop system constant, the loop system may be tuned by the variable inductance. In both cases the electrical symmetry of the loop system is not destroyed. The inductance of the closed resonido ant system, and hence the Wavelength of the loop system, is varied by Varying an inductance connectedin parallel with the loop cir- Referring more particularly to Figure 1 numeral lrepresents the loop circuit of a radio denser in parallel with said closed loop circuit and said connectlng means, and means for coupling sald radio compass system to a re- CGIVGI.

WILLIAM D. rouerrnin.

compass system and 2 represents the tuning condenser. Between the terminals of 1 and 2 and in parallel with l and 2 is. connected one of a plurality of fixed inductances, 4 and .5, (two are shown in this disclosure butagreater number may be used). 3 represents the output terminals for connecting 1 and; 2 and the associated ind-uctance toa receiver and amplifier. The inductances 4L and 5 are mounted in. the operating room in close proximity to the tuning condenser 2 and are shielded from the loopturns 1. There is,

' over a definite band of frequencies the shunt inductance l isconnected; in parallel with 1 theswitching arrangement 8 and tuning accomplished by varying the condenser 7. 'A

third definite band of frequenciesis provided for by the selection of ashunt inductancecoil 5 of; a. different inductance; value. The selecti'on of these or'othershunt i-nductances. may

be such that a continuous. and very broad band oi frequencies, with suitable overlaps if desirechis available. 7

Figure 2 shows the modification 03% this in.

. vention in which the shunt. inductance 4c is made variable over large Values of inductance.

Tuning may be accomplished in this case by varying the inductance denser 2 fixed. r

Itwill be understood that the above/description and accompanying drawings compre- Jhend'only the generaliand preferred modi.

i-ication oi the invention andthat various minor changes in detail of construction; proportion and arrangement of partsmay-be, wathin the scope of the appended claim and without; sacrificing any of the advantages of 7 my invent on.

The invention manufactured. and used by. or-for the GOVQ- TH- voiia closed loop circuit susceptible to the elecwent otthe United States for governmental purposes Without the payment to me of any royalty thereon ortherefor.

.Hav'ing described my invention 1 claim In a radio compass system, the combination tromagnetic component of an incoming wave, a "plurality of separate inductance coils of differing values of inductancainea-ns for shielding said coils from said closed loop. .cir-

cuit means for individually connecting said coilsin parallel with said loop circuit, a con herein described may. be

4 and keeping the con- I are 1 

